CRP001 (CONCEPTS OF PLANT DISEASES) Flashcards
1
Q
Structures of the pathogen found associated with the infected plant
A
Signs
2
Q
Actual evidence or proof of the presence of a pathogenic agent
A
Signs
3
Q
the suspected pathogen must always be present in the plant when diseases occur
A
Association
4
Q
PROOF OF PATHOGENICITY also called
A
Koch’s postulate
5
Q
causal organism must be isolated and grown in pure culture
A
Isolation
6
Q
the pure culture must be introduced to a healthy susceptible host to
produce the symptoms and signs of the disease
A
Inoculation
7
Q
the suspected causal organism must be re-isolated in pure culture from
the inoculated plant and must be identical to the original organism
A
Re-isolation
8
Q
Enumerate the Classification of Plant Diseases (4)
A
- According to the affected plant organ
- According to the symptom
- According to the type of affected plants
- According to type of pathogen that cause disease
9
Q
The more common non-parasitic causes of disease in plants are: (13)
A
- extremely high temperatures
- excessively low temperatures
- lack of oxygen
- unfavorable soil moisture relations
- nutrient deficiencies
- nutrient excesses
- mineral toxicities
- air pollutants
- toxicity of pesticides
- improper agricultural practices
- adverse meteorological conditions
- naturally occurring toxic chemicals
- too much or too little light
10
Q
Abiotic stress or injury (4)
A
- Non-living
- Not spread from diseased to healthy plants
- Non-infectious
- Knowledge of environmental factors before and during disease occurrence necessary for
correct diagnosis
11
Q
PARASITIC AGENTS OF PLANT DISEASES (7)
A
- Viruses and Viroids (subcellular entities)
- Bacteria and phytoplasmas (prokaryotes)
- Fungi and fungal-like protists
- Nematodes
- Parasitic flowering plants
- Protozoa
- Others
12
Q
Ultramicroscopic obligate parasites made up of nucleic acid and a protein coat.
A
Virus
13
Q
Virus:
The infectious part
A
Nucleic acid core (RNA or DNA)
14
Q
- Provide a protective sheath for the nucleic acid
- Facilitate the movement of virus from cell to cell
- For transmission of viruses by vectors
A
Protein coat
15
Q
What are the functions of the protein coat?
A
- Provide a protective sheath for the nucleic acid
- Facilitate the movement of virus from cell to cell
- For transmission of viruses by vectors
16
Q
Stable entities of low molecular weight RNA that can infect plant cells
A
Viroids
17
Q
They are much smaller than viruses and lack a protein sheath.
A
Viroids
18
Q
Shape of virus particle
A
- Spherical
- Bacilliform
- Cylindrical
- Bullet-shaped
- Elongate rod-shaped
- Flexible filaments
19
Q
viruses that attacks bacteria
A
Bacteriophages
20
Q
associated with an autonomous virus before it can cause infection or be
replicated in the host plant
A
Satellite virus
21
Q
Transmission and Spread of Viruses (8)
A
- Mechanical means
- By grafting
- By nematodes (as vectors)
- By certain soil-borne fungi (as vectors)
- By insects (as vectors)
- Through infected seeds
- Through infected vegetative planting materials
- Mites
22
Q
if the insect transmits the virus within seconds or minute after acquisition
A
Non-persistent
23
Q
Types of Virus transmission (4)
A
- Non-persistent
- Persistent
- Stylet-borne
- Circulation
24
Q
viruses that adhere to and are borne on the stylet of an insect that feeds on an infected plant
A
Stylet-borne
25
if the insect transmits the virus only after a latent period has elapsed after acquisition
and the vector remains capable of transmission for many days
Persistent
26
viruses that are swallowed by an insect passed through the blood and are returned to
the salivary glands before they can be transmitted by an insect
Circulation
27
Symptoms Caused by Virus
* Range from no symptoms to death of plants
* Local lesions
28
Systemic symptoms
* Mosaic
* Ringspot
* Excessive branching (Witches’ broom)
* Vein clearing
* Color Breaking
* Stunting
* Chlorosis
* Leaf curling
29
are generally stunted and yield less produce of usually poor quality
Virus-infected plants
30
If the plant is symptomless because of unfavorable environmental conditions, the symptoms
are said to be ______
masked
31
If no symptoms appear irrespective of the environment, then the infected plant is a
__________________
Symptomless carrier
32
are helpful to the bacteria in carrying the determinants for drug resistance, phage
resistance, UV resistance, survival in secondary habitats and for pathogenesis
Plasmids
33
Some bacteria have a ________ which is used for movement
Flagella
34
Characteristics of Plant Pathogenic Bacteria (5)
* Mostly rod-shaped
* Mostly aerobic
* Mostly flagellated
* Mostly Gram-negative
* Mostly non-spore forming
35
Symptoms Caused by Bacteria (6)
* Leaf Spot
* Soft Rot
* Blight
* Gall
* Canker
* Wilting
36
are prokaryotic microorganisms similar to bacteria, they have no cell walls
Mollicutes
37
Mollicutes are resistant to ___________
Penicillin
38
is a specialized propagative body which may be formed asexually by arising from
modified mycelial portions or sexually through the fusion of unlike celled (gametes)
Spore
39
The fungal plant pathogen's primary stored carbohydrate is ________
Glycogen
40
The mycelium may have ______ or _____ or may be continuous (__________).
Cross walls; septa; coenocytic
41
Septate mycelia may be (3)
uninucleate or binucleate or multinucleate
42
Each branch of a mycelium is called _____
Hypha
43
Mycelial growth occurs at the ___________
Hyphal tips
44
a specialized propagative body which may be formed asexually by arising from
modified mycelial portions or sexually through the fusion of unlike celled (gametes)
Spore
45
The only member of Kingdom Fungi that form motile cells (zoospores or gametes)
Chytridiomycota
46
sexual spores (Ascospores) formed within a sac known as ascus
Sac fungus
47
Produce non-motile asexual spores in sporangia
Zygomycota
48
Sexual reproduction is through an ascogonium (female spore) fertilized by an
antheridium or spermatium, a minute male spore
Ascomycota
49
the sexual or perfect stage
Teleomorph
50
the asexual or imperfect stage
Anamorph
51
Club and mushroom fungi
Basidiomycota
52
are thread-like unsegmented worms
which are usually elongated and cylindrical in shape
Nematodes
53
feed from the outside and only the stylet enters the plant cells
Ectoparasites
54
feed by burying the front part of the body into the host cells while the
posterior portion is outside the host
Semiendoparasites
55
the entire nematode body enters the plant cells while it feeds
Endoparasites
56
move from one part of the plant to another portion of the host or move from
the plant to the soil and back.
Migratory
57
attach themselves to the roots or burrow into the root
Sedentary
58
any part of the pathogen that can initiate disease
Inoculum
59
completed when the pathogen has passed through the initial cell wall or
entered the intercellular areas so that the pathogen is within the plant
Penetration
60
the deposition of inoculum unto or into an infection court
Inoculation
61
if the pathogen plays no active part in entering the host
plant
Passive Penetration
62
The pathogen directly participates as when the fungal spore
germinates, form a germ tube, an appressorium for attachment, and penetrates
through the intact host surface by forming an infection hypha or penetration
peg
Active Penetration
63
Occurs when the pathogen has become established in the
plant tissues and obtains nutrients from the host
Infection
64
Is the growth or movement of the pathogen through the host tissues
Colonization
65
the time from inoculation to the production of visible symptoms
Incubation
66
after the symptoms has advanced, signs or pathogen structures are usually formed on
the colonized surface of the host
Dissemination
67
* Survival phase
* Weakest link in the disease cycle
* Pathogen population is at its lowest
* Target for most control strategies
* The pathogen has therefore to tide over adverse conditions or survive until conditions
become once more favorable for pathogenesis.
Saprogenesis phase
68
One disease cycle in one crop growing season or one year
Monocyclic disease
69
2-30 disease cycles in one cropping season or one year
Polycyclic disease
70
is the study of disease development in plant populations
Epidemiology
71
refers to epidemics of plant diseases
Epiphytotic
72
is one that is native or indigenous to a particular place
Endemic disease
73
one which had been introduced from some other area
Exotic disease
74
one of worldwide or widespread occurrence throughout a continent
or a region
Pandemic disease
75
are those that occur at irregular interval
Sporadic disease
76
Fundamental principles for plant disease controlwere first classified by Whetzel (1929)
1. Exclusion
2. Eradication
3. Protection
4. Immunization
77
is the prevention of a “new pathogen” from being introduced into a locality where it is currently unknown.
Exclusion
78
Further advances in plant pathology led to development of newer methods. The National
Academy of Science (1968) has added two more principles.
5. Avoidance
6. Therapy
79
involves removal, elimination, or destruction of a pathogen from an area in which it is
established to reduce disease threat
Eradication
80
Involves the prevention of infection by putting a chemical barrier (protectant spray or dust)
between the pathogen and the suscept
Protection
81
involves modifying certain physiological or physical features of the host so that
it can repel infection, as in the breeding for disease resistance
Immunization or Host Plant Resistance
82
This involves avoiding disease by planting at time when, or in areas where inocula is absent
or ineffective due to environmental conditions
Avoidance
83
is the treatment of infected host plant, which is attempted in case of economically important
horticulture plants
Therapy
84
the use of chemicals to inactivate the pathogen
Chemotherapy
85
sometimes used to inactivate or inhibit virus development in infected plant
tissues so that newly developing tissue may be obtained which is free of pathogen
Heat
86
involves the exposure of diseased plants or parts of them to hot
water or high air temperatures for different periods of time.
Thermotheraphy
87
defined epidemics
as
an
increase
in
disease incidence within the plant population with time
Vander Plank (1963)
88
